Amniotic Fluid

Amniotic fluid

The fluid medium in which the fetus grows and develops inside the uterus.

Functions of amniotic fluid

During pregnancy

• Acts as a shock absorber protecting the fetus from the possible extraneous injury
• Maintains even temperature
• Fluid distends the amniotic sac and there by allows for growth and free movement  of the fetus
• It helps to prevent adhesion between the fetal parts and Amniotic sac.
• Its nutritive value is negligible as there is only small amount of  protein and salt. (water supply is quite adequate)

During labour

• Amnion and chorion combined to form hydrostatic wedge which helps in the dilation the uterine os and effacement of cervix.
• During U C it prevent marked interferance with the placental circulation so long as the membranes remains intact.
• Cont….
• Flushes the birth canal at the end of the first stage of labour.
• Antiseptic and bactericidal action protects the fetus from the ascending infection.
• origin

Fetal and maternal.

• It is secreted by amnion especially the part covering the placenta and umbilical cord.
• Transudate from maternal serum across the fetal membranes or from the maternal circulation.
• Cont…
• Transudate of fetal plasma through highly permeable fetal skin before it is keratinized at 20th week.
• Fetal urine also contributes to the volume from 10^th week. (water of the A F is exchanged every 3 hrs.)

Clinical importance

• As a measure of fetal wellbeing
• Normal amount at term approximately 1000ml
• If more than 2000-polyhydramnios
• If less than 200 ml-oligohydramnios

Volume of A F

• 50 ml at 12^th  week.
• 400 ml at 20^th week.
• Reaches the peak amount at 36 to 38^th  week –that is approximately 1000ml.
• Thereafter amount diminishes at term the it measures about600 to 800 ml.

Chemical property

• Faintly alkaline with low specific gravity.of 1.010.

Colour

• Straw coloured(exfoliated epidermal cells and lanugo)
• Turbid (presence of vernix caseosa)

Abnormal colours

• Green coloured
• Golden coloured
• Greenish yellow (saffron)
• Dark coloured
• Dark brown

Anatomical variation of placenta and cord

• Succenturiate lobe of placenta
• Circumvallate placenta
• Battledore insertion of the cord
• Velamentous insertion of the cord.
• Bipartite
• tripartite